PROBLEM TO BE SOLVED: To provide an air/water supply device of an endoscope with a water feed bottle that can wash away fluid and the like firmly stuck to an observation window by not only spraying water to the observation window but also forming an air-mixed spray state and, when an air feed operation is done after the spray operation, preventing air to be fed from being mixed with water and preventing an operators rhythm of operating the endoscope from being disturbed.SOLUTION: A changeover valve 30 provided in a water feed bottle 12 is formed with a spray vent hole 20 that causes pressurized air to flow in a water pipe 22 in the water feed bottle 12 and mixes it with water in the water pipe 22. The changeover valve can change over between: a state of causing the pressurized air in the water feed bottle 12 to flow from the spray vent hole 20 into the water feed pipe 22, mixing it with the water in the water feed pipe 22, and causing the water in a spray state to be sprayed to the observation window and a state of preventing the pressurized air in the water feed bottle 12 from flowing in the water feed pipe 22, feeding only storage water to the water feed pipe 22, and causing only water to be sprayed to the observation window.
